After a large earthquake, the evaluation of damage of structures is an important task for structural health assessment. Therefore, the structural health monitoring (SHM) has become major researches which focus in the area of structural dynamics. As we known, the presence of damage or deterioration in a structure can be detected by the changes in the natural frequencies of the structure. Furthermore mode shape changes can be categorized as damage localization 1. Besides, many damage detection algorithms based on the modal properties of structure such as modal frequencies, mode shapes, curvature mode shapes and modal flexibilities have been studied for several decades. However, in most algorithms, identifying the precise location and magnitude of the damage is difficult. If not completely impossible, the accuracy and reliability is not sufficient 2. Using only modal frequencies and their mode shapes changes to qualify damage seems very difficult to get the real damage in many previous studies. This research desires to test the applicability of mode-based damage assessment method to the real-size building, in order to give correlation between simulation models and real building with the changes in frequencies and mode shapes. The data of the simulations and E-defense Tests on the full-scale four-story steel building will be used to test this exiting method.